Question

embryological development
early
stage
gill
slits
tail
gill slits
tail
gills
forelimb
bud
gills
hind-limb
bud
hind-limb
bud
forelimb
bud
hind-limb
bud
gills
gills
late
stage
species q
species r
species s
species t
species u
sed on structural development, which two organisms appear to be most closely related?
a species q and species r, because they both have gills during late-stage development
b species s and species u, because they both have forelimb buds throughout development
c species r and species t, because they both have gill slits during early-stage development
d species s and species t, because they both have a tail during late-stage development

Explanation:

To determine the most closely related species, we analyze embryonic development similarities. Closely related species often have more similar developmental patterns.

• Option A: Species Q and R have gills in late stages, but many species have gills in early stages (a common ancestral trait), and their late - stage forms differ more.
• Option B: Species S and U having forelimb buds throughout is not a strong indicator as forelimb buds are a general developmental feature.
• Option C: Species R and T having gill slits in early stages is a common ancestral trait (many species have gill slits early), not a sign of close relation.
• Option D: Species S and T have a tail in late - stage development. The late - stage developmental similarities, especially in body form and the presence of a tail, suggest a closer evolutionary relationship as late - stage development is more species - specific.

Answer:

D. Species S and Species T, because they both have a tail during late - stage development